Most astronomical discoveries are made with a telescope. But one astounding discovery was made with pencil, paper, and a bit of mathematical genius.

The discovery was the planet Neptune. It was made by French astronomer Urbain Leverrier, who was born 200 years ago today.

Leverrier originally studied chemistry, but gave it up for mathematics and astronomy. He was on the staff of the Paris Observatory when he took on one of the most puzzling problems of the day: The orbit of the planet Uranus didn't match the predictions of Isaac Newton's laws of gravity.

Leverrier spent months working on the problem. He calculated that Uranus was being tugged by the gravity of an unseen planet. He even calculated the planet's position in the sky, and sent the information to the Berlin Observatory. On the night they received Leverrier's calculations, astronomers there found the planet -- just where Leverrier said it would be.

Leverrier then turned to a similar problem for the planet Mercury. He calculated that another planet -- called Vulcan -- orbited even closer to the Sun than Mercury did.

Astronomers across Europe began searching for the planet, but they never found it.

Leverrier wasn't wrong; he just didn't have the right tools. The discrepancy in Mercury's orbit was caused by the Sun, which "warps" the space around it. But that explanation awaited new laws of gravity devised by another mathematical genius: Albert Einstein.

Script by Damond Benningfield, Copyright 2011

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